The present invention relates to a transverse beam and means for preventing motion of the beam relative to a spar on which the beam is supported. The beam of the invention has particular use for supporting roof loads on a motor vehicle which is equipped with roof rails. At each of its end regions, the beam has a holding element having two clamping jaws which can be pulled toward each other by a clamping element for attaching the transverse beam to the longitudinal spars of the roof rails.
In a transverse beam of this type, known from German Utility Model 81 36 129, an adhesive force is produced by tightening turnbuckles which pull the clamping jaws of a holding element together, against the corresponding spar. This has disadvantages. Excessive clamping pressure can deform the spar surface, a notch effect, or can even lead to breaking of the clamping jaws. On the other hand, too low clamping pressure can permit the transverse beam supporting the roof load to shift in the longitudinal direction of the vehicle upon strong acceleration or deceleration of the vehicle. Such shifting of the beam can have serious consequences.
DE 33 01 706 A1 does not directly relate to a transverse beam of the type indicated above. But it shows that a roof luggage rack provided with support feet and clamping lugs can be attached on rain gutters which extend on both sides in the region of the upper edge of the roof of a motor vehicle. In order to prevent the roof luggage rack from slipping beyond the roof gutters upon hard braking or upon a collision of the vehicle with another vehicle or an obstacle, this known construction provides stop means on the roof rails for limiting shifting of the roof rack in the longitudinal direction of the vehicle.
Another known roof luggage rack for a motor vehicle, shown in DE 33 01 705 A1, is supported by support feet in the rain gutters extending on both sides in the region of the upper edge of the vehicle roof. This rack can be attached on the motor vehicle by clamping lugs which engage below the rain gutters and can be clamped with the support feet. It is designed so that it is reliably held on the roof of the motor vehicle even upon strong deceleration or acceleration of the vehicle. For this purpose, blocking means are provided on the roof luggage rack. These act between the rack and the rain gutters to prevent forward shifting of the roof luggage rack in the longitudinal direction of the vehicle.